Hindawi Publishing Corporation Computational Biology Journal Volume 2015, Article ID 427217, 10 pages http://dx.doi.org/10.1155/2015/427217 Research Article Structural Differences in KIR3DL1 and LILRB1 Interaction with HLA-B and the Loading Peptide Polymorphisms: In Silico Evidences Alba Grifoni,1,2 Atanas Patronov,1 Carla Montesano,2 Vittorio Colizzi,2 and Massimo Amicosante1,3 1 ProxAgen Ltd., 63 Shipchenski Prohod, 1574 Sofia, Bulgaria 2Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 18, 00133 Rome, Italy 3Department of Biomedicine and Prevention, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy Correspondence should be addressed to Alba Grifoni; [email protected] Received 24 August 2015; Revised 21 October 2015; Accepted 26 October 2015 Academic Editor: Jinn Moon Yang Copyright © 2015 Alba Grifoni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. KIR3DL1 and LILRB1 interact with HLA class I. Using KIR3DL1/HLA-B interaction to set up the procedure, structural immune- informatics approaches have been performed in LILRB1/HLA-B alleles’ combination also considering the contribution of the HLA bound peptide. All KIR3DL1 alleles interact strongly with HLA-B alleles carrying Bw4 epitope and negative charged amino acid residues in peptide position P8 disrupt KIR3DL1 binding. HLA-B alleles carrying Ile 194 show a higher strength of interaction with LILRB1 in all the analyzed haplotypes. Finally, we hypothesize a contribution of the amino acid at position 1 of the HLA bound peptide in the modulation of HLA-B/LILRB1 interaction. 1. Introduction We have previously reported a system for analyzing the ∗ interaction between KIR3DL1 001 allele and different HLA- The modulation of NK cells’ immune response is mediated by B alleles by using a docking approach recently confirmed by inhibitory and activating receptors expressed on their surface experimental data [14, 16, 18]. Due to the fact that interaction [1–4]. Among them, KIR3DL1 and LILRB1 have shown the patterns in the context of different HLA/KIR3DL1 variants capability to recognize HLA class I molecules. still need to be addressed the use of the same in silico approach KIR3DL1 is able to interact with HLA class I molecules couldshednewlightontheHLA/KIR3DL1interactionthat carrying Bw4 epitope, while no interaction has been observed has not yet been evaluated. in the presence of Bw6 epitope. KIR3DL1 alleles are divided LILRB1/ILT-2/LIR1 is an inhibitory receptor expressed on into three subclassifications depending on NK surface expres- a fraction of NK cells, / and / T-cells, CD19+ B cells, ∗ ∗ ∗ ∗ ∗ sion: high expressive ( 001, 002, 008, 009, 015,and CD14+ monocytes, and HLA-DRhigh dendritic cells [19, 20]. ∗ ∗ ∗ ∗ 020), low expressive ( 005, 007), and nonexpressive ( 004) In NK cells, the block of the LILRB1 receptor has shown [5, 6]. Association studies between KIR3DL1 alleles and infec- the restoration of NK cell cytotoxic activity, suggesting a key tious diseases have been extensively reported in the past years. roleintheimmuneregulation[21]. In this context, high expressive and nonexpressive alleles lead LILRB1 is composed by four Ig-domains (D1–D4 form to a delayed HIV infection progression in the presence of N to C terminal) and binds HLA-A, HLA-B, and HLA-G HLA-B carrying Bw4 epitope [7]. These results encouraged with high affinity [22–26]. LILRB1 interacts with HLA class the evaluation of HLA/KIR3DL1 pattern of interaction [8– Inonpolymorphic3-domain [27] and 2-microglobulin 11]. Beside the strong interaction with HLA Bw4 epitope, domain [28, 29]. structuralevidenceshavealsoshownarolefortheHLA Amino acids Ala 193 and Val 194 were associated with bound peptide in the recognition by KIR3DL1 [12–17]. lower binding property of LILRB1 even though apparently 2 Computational Biology Journal Table 1: List of KIR3DL1 alleles selected for immune-informatics approach. Alleles were selected depending on amino acid polymorphisms ∗ with respect to the reference allele KIR3DL1 001 and allele frequency in general population [36, 37]. KIR3DL1 polymorphic amino acid position (7–292) Expression KIR3DL1 alleles 47 54 58 92 182 283 ∗ KIR3DL1 001 IISVPW ∗ High KIR3DL1 009 V I GMPW ∗ KIR3DL1 015# VLSVPW ∗ KIR3DL1 007# VLSVPW Low ∗ KIR3DL1 005 IISVSL #007 and 015 share the same amino acid polymorphisms and have been analyzed together. the only presence of Val 194 did not influence the LILRB1 Table 2: List of LILRB1 haplotypes selected for immune-informatics recognition [30]. We recently reported a direct association approach. The LILRB1 haplotypes are distinguished by the following of Val 194 in HIV delayed progression due to a weaker amino acid polymorphisms in the mature protein sequence in interaction with LILRB1 receptor [31]. Thus, HLA amino acid accordance with previous classifications [33, 34]. position 194 could have a role in the modulation of LILRB1 LILRB1 amino acid position interaction. LILRB1 haplotype Twelve LILRB1 polymorphisms located between 45 70 119 132 -634A>Gtoc.464G>T constitute three major haplotypes LILRB1.01 L A I S in Japan (LIR1.PE01, LIR1.PE02, and LIR1.PE03). Previous LILRB1.02 P T T I studies have associated LILRB1 haplotypes with viral disease LILRB1.03 P A I I progression and variation of NK cells’ membrane expression [32–34]. In addition, the HLA bound peptide has shown to contribute in the interaction [35], suggesting a role in considered, as previously reported [18]. KIR3DL1 alleles have the modulation of the strength of interaction with LILRB1 been selected depending on human population frequency similar to the one observed in KIR3DL1. However, peptide and coded amino acid polymorphisms (Table 1). Among ∗ ∗ position and amino acid variants able to modulate the them, KIR3DL1 015 and KIR3DL1 007 have been analyzed LILRB1 binding have not yet been assessed. The aim of together as they share the same amino acid polymorphisms this study is to evaluate the interaction pattern of KIR3DL1 in the coding region (Table 1). HLA-B peptides with similar and LILRB1 receptors with HLA class I molecules and the EC50 (200 nM) were selected as references from IEDB contribution of the bound peptide and its implication from database [39] as previously reported [18]. an immunological point of view. In this context, structural immune-informatics approaches have been performed 2.2. HLA/LILRB1 Interaction Study. HLA-B alleles have been using homology modeling and docking strategies to obtain divided depending on carrying Val or Ile 194 and on their HLA-B/KIR3DL1 and HLA-B/LILRB1 models that take supertype [38], as previously reported [18]. In order to com- into consideration the most frequent allele’s combination pare different HLA-B alleles interacting with different LILRB1 in human population. Models were subjected to energy ΔΔ receptor alleles, we focused our study on the three known minimization and analyzed for energy, number of haplotypes (LILRB1.01, LILRB1.02, and LILRB1.03) carrying contacts (number of atoms in the interactive surface), amino acid variants located in amino acid positions 45, 70, and VdW and H-bond, using a combination of utilized 119, and 132 of the mature protein sequence within known public tools. Our results are in agreement with previous LILRB1 alleles and located on the HLA-LILRB1 interaction findings on HLA/KIRDL1 interaction and can be extended binding site [33, 34] (Table 2). to all the alleles’ combination of the study. In HLA/LILRB1 interaction context, we extended our previous evidence for HLA Ile/Val 194 contribution in the interaction with LILRB1. 2.3. Molecular Modeling and Analysis. Homology model- In addition, a contribution of the bound peptide at relative ing strategy has been performed as previously reported position 1 capable to modulate HLA-B/LILRB1 interaction is [18] and analysis strategy has been schematized as illus- hypothesized. trated in the flowchart (Figure 1). Specifically, KIR3DL1 and LILRB1 studies have been performed using the HLA- 3 1∗001 2. Material and Methods B57/KIR DL (PDBID:3HV8)andHLA-A2LILRB1 (PDB ID: 1P7Q) cocrystallization structures as templates, 2.1. HLA/KIR3DL1 Interaction Study. HLA-B alleles have respectively. MOTIF alignments [40] of the HLA-B structures been divided depending on carrying Bw4/Bw6 epitope with the template structures have been performed followed ∗ ∗ ∗ (Bw4: HLA-B 27:05, HLA-B 51:01, HLA-B 57:01, and by HLA-B replacement. HLA bound peptide complexes have ∗ ∗ ∗ HLA-B 58:01; Bw6: HLA-B 07:02, HLA-B 14:02, and been generated through single point amino acid substitution ∗ HLA-B 35:01). HLA supertype [38] and HLA allele (SAS) in the peptide. KIR3DL1 alleles and LILRB1 haplotypes frequency in different human population [36] have been have been obtained through amino acid mutation starting Computational Biology Journal 3 Steps FASTA sequences from Crystal structure IMGT HLA database and (1) Generation of HLA-B PDB database modeling with Swiss Model crystal structure and models 7 HLA-B structure aligned and substituted to the HLA (2) HLA-B substitution in molecules presented in the crystal models used as crystal template models templates (PDB ID: 3HV8 and 1P7Q) ∗ Single point mutation in KIR3DL1 001 allele and LILRB1.01 (3) Generation of different haplotype in order to obtain an overall number of 35 HLA- KIR3DL1 alleles and B/KIR3DL1 and 21 HLA-B/LILRB1 models LILRB1 haplotypes Single amino acid substitution (SAS) in the bond peptide for (4) Generation of different all the peptide amino acid positions in order to obtain an bond peptides overall number of 6300 HLA-B/KIR3DL1 and 3780 HLA- B/LILRB1 models (5) Minimization of the All the models are subjected to energy minimization models through NOVA ff (6) Data analysis ΔΔG, number of contacts, and H-bond calculation Figure 1: Flowchart to illustrate the analyzing strategy.